Junction boxes for shielded cables such as data transmission cables are not new per se. German Patent DE 4,234,451 and U.S. Pat. No. 5,447,441 show prior art junction boxes. These boxes generally comprise a housing made up of an upper part and a lower part. The housing holds a connecting terminal for the wires of at least one cable and at least one jack into which a terminal plug can be inserted. The jacks and the connecting terminals are connected to each other via a printed circuit board (PCB). The housing surrounds and thus shields the PCB, the jacks, and the connecting terminals. In these boxes, the shielding of the cable is brought into conductive contact with the metal housing and a continuous ground connection for the shielding function is established from the cable shielding via the lower and upper parts of the housing and the PCB to the jack. The exposed parts of the wires, the connecting terminal and the PCB are completely enclosed and shielded, so that no stray radiation or stray signals can escape from the junction box to the ambient environment and no interfering signals from the outside can enter the junction box and to be picked up.